A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work. The heat engines form the very crux for the ever useful and ubiquitous Internal Combustion Engines and this series of articles delve into the very basics of the working of the Internal combustion engines. A firm understanding of Internal Combustion Engines cannot be possible without grounding on Heat engines and concepts of Energy.

Heat engines are classified into two broad types:

External Combustion Engines and

Internal Combustion Engines

In an external combustion engine, the products of combustion of and air and fuel transfer the heat generated to a second fluid which is the working fluid of the cycle ( like water is for a steam engine, where the heat is used to generate steam from water, which in turn is used to power the piston or a turbine).

Another good example of an External Combustion Engine is a closed Cycle gas turbine wherein the heat generated from a closed furnace is transferred to gas, usually air, which is then used in the gas turbine.

In an Internal Combustion Engine, the products of combustion would directly move the piston of the engine. Gasoline, Diesel, Wankel engines and open gas turbines are all examples of an Internal Combustion Engine.

Advantages of IC Engines over EC engines

The IC engines are generally simpler and offer much greater mechanical simplicity compared to the EC engines.

The IC engines have a lower weight -to-output ratio due to the absence of auxiliary units like boilers and condensers that are required for an External Combustion Engine.

The cost of manufacturing an IC engine is much lesser owing to the ease and standardization in production and

Higher overall efficiency in operations as compared to the EC Engines because most of it is within the engine and not much energy produced is lost.

EC engines cannot be used for smaller requirements like in transportation. But IC engines can be used due to their compact size.